Optical storage technology has evolved from the compact disc (CD) and laser disc (LD) to far denser types such as digital versatile disc (DVD) and blue laser formats such as Blu-ray. Many optical devices capable of reading the newer, denser media types are also designed to read lower capacity media types such as CDs. This backward compatibility comes at a price, however, because the low- and high-density media types require optical systems having different parameters such as numerical aperture (NA) and laser diode wavelength (λ). An optical device capable of reading multiple media types must, therefore, adjust (focus) the various optical systems (combinations of laser and optics) in succession until it finds the correct one for a particular optical disc. In such optical devices, the start-up time increases with the number of optical storage media types supported.
It is thus apparent that there is a need in the art for an improved indication to enhance the detection of the type of an optical storage medium or other necessary information.